Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$200.72	12.636%	$226.083	$226.08	$226.10	$226.10
Purchase #2	$59.79	7.865%	$64.4925	$64.49	$64.50	$64.50
Purchase #3	$69.73	9.328%	$76.2344	$76.23	$76.25	$76.20
Purchase #4	$231.72	10.856%	$256.8755	$256.88	$256.90	$256.90
Purchase #5	$69.96	11.808%	$78.2209	$78.22	$78.20	$78.20
Purchase #6	$201.47	5.833%	$213.2217	$213.22	$213.20	$213.20
Purchase #7	$95.93	6.563%	$102.2259	$102.23	$102.25	$102.20
7 purchase totals =	$929.32		$1,017.3539	$1,017.35	$1,017.40	$1,017.30